Thermal detector, thermal detection device, electronic instrument, and thermal detector manufacturing method

ABSTRACT

A thermal detector includes a substrate; a support member supported on the substrate interposed by a cavity; a heat-detecting element formed on the support member and having a pyroelectric material layer disposed between a lower electrode and an upper electrode; a light-absorbing layer formed on the heat-detecting element; and a thermal transfer member including a connecting portion connected to the heat-detecting element and a thermal collecting portion disposed inside the light-absorbing layer and having a surface area larger than that of the connecting portion in plan view, the thermal collecting portion being optically transmissive at least with respect to light of a prescribed wavelength. The lower electrode has an extending portion extending around the pyroelectric material layer in plan view, and the extending portion has light-reflecting properties by which at least a part of the light transmitted through the thermal collecting portion of the thermal transfer member is reflected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2010-286334 filed on Dec. 22, 2010, Japanese Patent Application No.2010-289491 filed on Dec. 27, 2010, Japanese Patent Application No.2010-289492 filed on Dec. 27, 2010, Japanese Patent Application No.2011-012060 filed on Jan. 24, 2011 and Japanese Patent Application No.2011-036886 filed on Feb. 23, 2011. The entire disclosures of JapanesePatent Application Nos. 2010-286334, 2010-289491, 2010-289492,2011-012060 and 2011-036886 are hereby incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a thermal detector, a thermal detectiondevice, an electronic instrument, and a thermal detector manufacturingmethod.

2. Related Art

Thermal detection devices are known as light sensors. Thermo-opticaldetectors absorb light that has been emitted from an object in alight-absorbing layer, convert the light to heat, and measure the changein temperature with a heat-detecting element. Thermo-optical detectorsinclude thermopiles that directly detect the increase in temperatureaccompanying light absorption, pyroelectric-type elements that detect achange in electrical polarity, and bolometers that detect the increasein temperature as a change in resistance. Thermo-optical detectors havea characteristically wide wavelength range over which measurements canbe made. In recent years, semiconductor fabrication technologies (e.g.,MEMS technologies) have been used, and the production of smaller-scalethermal detectors has been attempted.

In order to increase detection sensitivity and improve response inthermal detectors, it is critical to efficiently transfer the heat thatis generated in the light-absorbing layer to the heat-detecting element.

The structure of a heat-detecting element for improving thermal transferefficiency is described, for example, in Japanese Patent No. 3339276.The infrared detecting element described in Japanese Patent No. 3339276(herein referred to as a thermopile-type infrared detecting element) hasa highly thermally conducting layer that is provided between an infraredlight sensing part and an infrared light absorbing layer. Specifically,a membrane is formed over a cavity, and the membrane is supported on thesurrounding substrate by protruding beams that are provided at the fourcorners. The center membrane portion has a highly thermally conductinglayer and an infrared light absorbing layer, and the edge portions havethermopile elements. In addition, the highly thermally conducting layeris made from a material having excellent infrared light reflectance,such as aluminum or gold.

SUMMARY

In addition, with the infrared light detecting element described inJapanese Patent No. 3339276, a high thermal transfer member is providedunder the light-absorbing layer, but the heat-detecting element is notprovided below the light-absorbing layer and the high thermal conductionmember. The infrared light absorbing layer is at a position that isseparated from the infrared sensing part heat-detecting element, and sothe heat that is generated in the infrared light absorbing layer cannotbe supplied, in some cases, directly to the heat-detecting elementinfrared light sensing part.

With the infrared light solid-state image capture element described inJapanese Patent Application Republication No. 99/31471, an insulatinglayer that constitutes an infrared light-absorbing part is in a positionthat is separated from the temperature detector, and so the heat that isgenerated in the insulating layer of the infrared light absorbing part,in some cases, cannot be supplied directly to the temperature detector.

In accordance with at least one aspect of the present invention, it ispossible to increase the detection sensitivity of a thermal detector.

A thermal detector according to one aspect of the present inventionincludes a substrate, a support member, a heat-detecting element, alight-absorbing layer and a thermal transfer member. The support memberis supported on the substrate so that a cavity is formed between thesubstrate and the support member. The heat-detecting element is formedon the support member and having a structure in which a pyroelectricmaterial layer is disposed between a lower electrode and an upperelectrode. The light-absorbing layer is formed on the heat-detectingelement. The thermal transfer member includes a connecting portionconnected to the heat-detecting element and a thermal collecting portiondisposed inside the light-absorbing layer and having a surface arealarger than a surface area of the connecting portion as seen in planview, the thermal collecting portion being optically transmissive atleast with respect to light of a prescribed wavelength. The lowerelectrode has an extending portion extending around the pyroelectricmaterial layer as seen in plan view. The extending portion haslight-reflecting properties by which at least a part of the lighttransmitted through the thermal collecting portion of the thermaltransfer member is reflected.

In the thermal detector of the aspect described above, for example, apart of the light that is incident on the thermal detector (for example,infrared light) is first absorbed by a second light-absorbing layer, andthe remainder thereof arrives at the thermal transfer member withoutbeing absorbed. The thermal transfer member, being opticallytransmissive to light of at least part of a wavelength region, can betranslucent in, for example, an infrared region (for example, a farinfrared region). In the thermal transfer member, for example, a part ofthe light that has arrived is reflected, and the remainder thereof istransmitted through the thermal transfer member. A part of the lightthat is transmitted through the thermal transfer member is absorbed by afirst light-absorbing layer, and the remaining light thereof arrives atthe heat-detecting element.

The heat-detecting element is formed on the support member. Herein, theexpression “on . . . ” may refer to “directly above,” or mayalternatively refer to the upper part (in cases in which another layeris interposed). A similarly broad interpretation is possible in otherplaces as well.

The lower electrode of the heat-detecting element comprises theextending portion that extends on the support member; this extendingportion has light-reflecting properties. Namely, the lower electrodecomprises a material with excellent conductivity (for example, ametallic material); the light reflectance of metallic materials and thelike is generally high. Accordingly, much of the light that is incidenton the surface of the extending portion of the lower electrode, which isa constituent element of the heat-detecting element, is reflected, thisreflected light being absorbed in either the first light-absorbing layeror the second light-absorbing layer. The reflected light can accordinglybe used without waste, and can be converted to heat. A part of the lightthat arrives at the surface of the support member may also possibly bereflected and absorbed in either the first light-absorbing layer or thesecond light-absorbing layer. In this regard as well, the incident lightcan be used efficiently.

The lower electrode (which comprises a metallic material or the like),having high thermal conductivity as well, therefore also exerts theeffect of transferring to the pyroelectric material layer heat that, forexample, has been generated at places distant from the pyroelectricmaterial layer in a light-absorbing layer. That is, the lower electrode,for example, extends broadly on the support member, and is thereforecapable of efficiently transferring heat generated in a broad range inthe light-absorbing layers to the pyroelectric material layer. In thisregard, it can be said that the lower electrode also serves as a thermaltransfer member (that is, as a thermal transfer member which can be saidto be, for example, a second thermal transfer member, distinct from thethermal transfer member formed on the upper part of the heat-detectingelement, which can then be said to be the first thermal transfermember).

The thermal transfer member comprises a material that is opticallytransmissive (for example, semi-transmissive), and comprises aconnecting portion and a thermal collecting portion that has a greatersurface area than that of the connecting portion in plan view, thethermal collecting portion being formed on the heat-detecting element.The thermal collecting portion of the thermal transfer member is taskedwith collecting heat that, for example, has been generated in a regionhaving a broad range, and transferring the same to the heat-detectingelement. Any metallic compound that, for example, has favourable thermalconductivity and is optically translucent (for example, AlN or AlO_(x))can be used for the thermal transfer member.

The following is an example of how, in a case in which the incidentlight exhibits such behaviour as described above, heat is generated inthe first light-absorbing layer and the second light-absorbing layer,and of how the generated heat is transferred to the heat-detectingelement. Namely, a part of the light that is incident on the thermaldetector is first absorbed in the second light-absorbing layer, heatthen being generated in the second light-absorbing layer. Light that isreflected by the thermal transfer member is also absorbed in the secondlight-absorbing layer, heat thereby being generated in the secondlight-absorbing layer.

A part of the light that is transmitted through (passes through) thethermal transfer member is also absorbed in the first light-absorbinglayer, thus generating heat. Much of (for example, the majority of) thelight that arrives at the extending portion of the lower electrode isalso reflected on the surface thereof and is absorbed in at least one ofeither the first light-absorbing layer or the second light-absorbinglayer, heat being thereby generated in the first light-absorbing layeror second light absorbing layer. The light that is reflected by thesurface of the support member is also absorbed in at least one of eitherthe first light-absorbing layer or the second light-absorbing layer,heat being thereby generated in the first light-absorbing layer orsecond light-absorbing layer.

The heat that has been generated by the second light-absorbing layer isthen transferred efficiently through the thermal transfer member to theheat-detecting element, and the heat that has been generated by thefirst light-absorbing layer is efficiently transferred, either directlyor via the thermal transfer member, to the heat-detecting element.Specifically, the thermal collecting portion of the thermal transfermember is formed so that it covers a large region of the heat-detectingelement, and thus most of the heat that has been generated by the firstlight-absorbing layer and the second light-absorbing layer can betransferred efficiently to the heat-detecting element, regardless of thesite at which it was generated. For example, even heat that has beengenerated at locations that are distant from the heat-detecting elementcan be efficiently transferred to the heat-detecting element via thethermal transfer member having high thermal conductivity.

Because the collecting portion of the thermal transfer member and theheat-detecting element are connected by the connecting portion of thethermal transfer member, the heat that is transferred via the thermalcollecting portion or the thermal transfer member can be directlytransferred to the heat-detecting element via the connecting portion.Moreover, because the heat-detecting element is positioned below thethermal transfer member (provided in an overlapping position as seen inplan view), for example, it is possible to connect the middle part ofthe thermal transfer member and the heat-detecting element by theshortest possible length, as seen in plan view. Thus, the loss occurringwith heat transfer can be decreased, and an increase in footprint can beminimized.

In addition, in this aspect, absorption efficiency is increased becauseheat is generated by a two-layer light-absorbing film. Moreover, theheat can be directly transferred to the heat-detecting element via thefirst light-absorbing layer. Thus, in comparison to the infrared lightsolid-state image capture element described in Japanese PatentApplication Republication No. 99/31471 and the infrared light detectionelement described in Japanese Patent No. 3339276, the detectionsensitivity of the thermal detector can be increased. Moreover, in thisaspect, the heat-detecting element is connected to the thermal transfermember, and the response rate is thus high, as with the infraredlight-detecting element described in Japanese Patent No. 3339276. Inthis aspect, because the thermal transfer member is directly connectedto the heat detecting element, a higher response rate can be obtained incomparison to the infrared light solid state image capture elementdescribed in Japanese Patent Application Republication No. 99/31471.

In another aspect of the thermal detector of the present invention, thelight-absorbing layer is preferably disposed on the support memberaround the heat-detecting element.

According to the aspect described above, the light-absorbing layers areformed around the heat-detecting element in plan view. Heat that hasbeen generated in a broad range on the light-absorbing layers is therebyeffectively transferred to the heat-detecting element, either directly,or indirectly through the thermal transfer member. The thermal detectorcan accordingly detect light at an even higher degree of sensitivity.The thermal detector also has a further improved response speed.

In another aspect of the thermal detector of the present invention, thelight-absorbing layer preferably has a first light-absorbing layercontacting the thermal transfer member and disposed between the thermaltransfer member and the extending portion of the lower electrode of theheat-detecting element, and a second light-absorbing layer contactingthe thermal transfer member and disposed on the thermal transfer member.

The aspect described above, being provided with the firstlight-absorbing layer and the second light-absorbing layer as thelight-absorbing layers, utilizes a configuration in which the thermalcollecting portion of the thermal transfer member is sandwiched by thetwo light-absorbing layers. Heat that is generated in a broad range onthe first light-absorbing layer and the second light-absorbing layer isefficiently transferred to the heat-detecting element, either directly,or indirectly through the thermal transfer member. Moreover, the lightof the incident light that is reflected by the thermal transfer membercan be absorbed by the second light-absorbing layer, which is the upperlayer, and the light that is transmitted through the thermal transfermember can be absorbed by the first light-absorbing layer, which is thelower layer.

According to the thermal detector of this aspect, the heat that has beengenerated in a broad range in the (plurality of) two light-absorbinglayers can be efficiently transferred to the heat-detecting element,and, accordingly, a small thermal detector can detect light withsignificantly improved sensitivity. Further, because the time requiredto transfer heat is curtailed, the thermal detector can have a fasterresponse speed.

In another aspect of the thermal detector of the present invention, afirst optical resonator for a first wavelength is preferably formedbetween a surface of the extending portion of the lower electrode and anupper surface of the second light-absorbing layer, and a second opticalresonator for a second wavelength that is different from the firstwavelength is preferably formed between a lower surface of the secondlight-absorbing layer and the upper surface of the secondlight-absorbing layer.

This aspect is configured such that the film thickness of eachlight-absorbing layer is adjusted to provide two optical resonatorshaving different resonance wavelengths. The first optical resonator forthe first wavelength is formed between the upper surface of the secondlight-absorbing layer and the surface of the extending portion of thelower electrode, which is formed on the support member and is aconstituent element of the thermal detector. The light that is reflectedby the surface of the extending portion of the lower electrode isabsorbed in at least one of either the first light-absorbing layer orthe second light-absorbing layer, but the first optical resonator isconstituted such that, at this time, each light-absorbing layer has ahigh effective absorptivity. The lower electrode comprises a materialthat has excellent conductivity (for example, a metallic material); thelight reflectance of metallic materials and the like is generally high.Accordingly, much of the light that is incident on the surface of theextending member can be reflected upwards. It is accordingly easy tocreate optical resonances.

Herein, the first optical resonator can be, for example, a so-called λ/4optical resonator. That is, the film thickness of the firstlight-absorbing layer and the second light-absorbing layer may beadjusted such that the distance between the surface of an extendingportion RX of a lower electrode (first electrode) 234 of a pyroelectriccapacitor 230 and the upper surface of the second light-absorbing layersatisfies the relationship n·(λ1/4) (n is an integer equal to or greaterthan 1), where λ1 is the first wavelength. The film thickness of thelower electrode can be made so thin that the film thickness can beignored; in this case, the total film thickness of the firstlight-absorbing layer and the second light-absorbing layer may satisfythe relationship n·(λ1/4) (n is an integer equal to or greater than 1).The light of the wavelength λ1 that is incident and the light of thewavelength λ1 that is reflected by the surface of the support member arethereby cancelled out by mutual interference, thus increasing theeffective absorptivity in the first light-absorbing layer and the secondlight-absorbing layer.

Moreover, as described above, the light that has been reflected by thethermal transfer member is absorbed by the second light-absorbing layer,and the effective absorption in the second light-absorbing layer can beincreased, in this case, by providing a second optical resonator. Forexample, a so-called λ/4 optical resonator may be used as the secondoptical resonator.

Specifically, taking the second wavelength as λ2, the second opticalresonator can be constituted by setting the distance between the bottomsurface of the second light-absorbing layer and the top surface of thesecond light-absorbing layer (specifically, the film thickness of thesecond light-absorbing layer) at n·(λ2/4). As a result, incident lightof wavelength λ2 and light of wavelength λ2 that has been reflected bythe bottom surface of the second light-absorbing layer (interfacebetween the first light-absorbing layer and second light-absorbinglayer) are canceled out due to mutual interference, thereby increasingthe effective absorption at the second light-absorbing layer.

According to this aspect, because resonance peaks are created in twodifferent wavelengths, the band of wavelengths (wavelength width) inwhich the thermal detector is able to detect light can be widened. Also,the light-reflecting layer and the thermal collecting portion of thethermal transfer member are disposed in parallel with each other. Aparallel between the upper surface of the light-reflecting layer and theupper surface of the second light-absorbing layer is accordinglymaintained.

In another aspect of the thermal detector of the present invention, thethermal transfer member preferably also serves as wiring thatelectrically connects the heat-detecting element to another element.

The thermal transfer member, as described above, can be constituted by ametal compound such as AlN or AlO_(x), but a material having metal as aprimary component is preferred, due to its favorable electricalconductivity, and the thermal transfer member may also be used as wiring(or a portion of the wiring) that connects the heat-detecting elementwith other elements. By using the thermal transfer member as wiring, theproduction steps can be simplified, because it is not necessary toprovide the wiring separately.

A thermal detection device according to another aspect of the presentinvention includes a plurality of the thermal detectors described in anyof the aspects above disposed two-dimensionally.

As a result, a thermal detection device (thermal-type optical arraysensor) is realized in which a plurality of the thermal detectors(thermo-optical detection elements) have been disposed two-dimensionally(e.g., disposed in an array formed along two perpendicular axes).

An electronic instrument according to another aspect of the presentinvention comprises the thermal detector described in any of the aspectsabove and a control part configured to process an output of the thermaldetector.

All of the thermal detectors described above have high detectionsensitivity, and thus the performance of the electronic instruments thatcontain these thermal detectors is improved. Examples of electronicinstruments include infrared sensor devices, thermographic devices,on-board automotive night-vision cameras, and surveillance cameras. Thecontrol part may be constituted, for example, by an image processingpart or a CPU.

A thermal detector manufacturing method according to another aspect ofthe present invention includes: forming a structure including aninsulating layer on a surface of a substrate; forming a sacrificiallayer on the structure including the insulating layer; forming a supportmember on the sacrificial layer; forming on the support member aheat-detecting element having a structure in which a pyroelectricmaterial layer is disposed between a lower electrode and an upperelectrode, the lower electrode having an extending portion extendingaround the pyroelectric material layer as seen in plan view, and theextending portion having light-reflecting properties by which arrivinglight is reflected; forming a first light-absorbing layer so as to coverthe heat-detecting element, and planarizing the first light-absorbinglayer; forming a contact hole in a portion of the first light-absorbinglayer, subsequently forming a material layer which is thermallyconductive and optically transmissive at least with respect to light ofa prescribed wavelength, and patterning the material layer to form athermal transfer member having a connecting portion that connects to theheat-detecting element and a thermal collecting portion having a surfacearea greater than that of the connecting portion as seen in plan view;forming a second light-absorbing layer on the first light-absorbinglayer; patterning the first light-absorbing layer and the secondlight-absorbing layer; patterning the support member; and removing thesacrificial layer to form a cavity between the support member and thestructure including the insulating layer formed on the surface of thesubstrate.

According to the aspect described above, the main surface of thesubstrate is laminated with a multilayer structure including inter-layerinsulating layers, the sacrificial layer, and the support member, andthe support member is also laminated with the heat-detecting elementincluding the lower electrode having the light-reflecting properties(that is, the lower electrode serving as a light-reflecting member), thefirst light-absorbing layer, the thermal transfer member, and the secondlight-absorbing layer. A planarization treatment is used to planarizethe upper surface of the first light-absorbing layer. The firstlight-absorbing layer is also provided with a contact hole, theconnecting portion of the thermal transfer member being embedded in thiscontact hole. The thermal collecting portion of the thermal transfermember, provided on the first light-absorbing layer, is connected to theheat-detecting element (for example, to an electrode on a pyroelectriccapacitor) via the connecting portion. According to this aspect, asemiconductor manufacturing technology (for example, MEMS technology)can be used to achieve a thermal detector that is both small and detectswith a high degree of sensitivity. Also, it is preferable that thelight-reflecting layer and the thermal collecting portion of the thermaltransfer member be disposed in parallel with each other. A parallelbetween the upper surface of the light-reflecting layer and the uppersurface of the second light-absorbing layer is thereby maintained.

In accordance with at last one of the aspects of the present invention,for example, it is possible to additionally increase the detectionsensitivity of the thermal detector.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1A is a schematic top plan view of an example of a thermal detectoraccording one embodiment.

FIG. 1B is a sectional view of the thermal detector as taken along asection line A-A′ in FIG. 1A.

FIG. 2A is a diagram showing an example of the spectral characteristics(light-reflecting characteristics and light-transmissioncharacteristics) of an alumina plate in the far-infrared wavelengthrange.

FIG. 2B is a diagram showing an example of the detection sensitivity ofthe thermal detector having a double optical resonator configuration.

FIGS. 3A to 3E are diagrams showing the steps for forming the firstlight-absorbing layer in the thermal detector manufacturing method.

FIGS. 4A to 4C are diagrams showing the steps for patterning the firstlight-absorbing layer and the second light-absorbing layer in thethermal detector manufacturing method.

FIGS. 5A and 5B are diagrams showing the steps for completion of thethermal detector in the thermal detector manufacturing method.

FIG. 6 is a diagram showing another example of the thermal detector.

FIG. 7 is a circuit diagram showing an example of the circuitconfiguration of a thermal detection device (thermal detector array).

FIG. 8 is a diagram showing an example of the configuration of anelectronic instrument.

FIG. 9 is a diagram showing another example of the configuration of anelectronic instrument.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments of the present invention are described below. Thematter of the present invention described in the claims is not undulylimited by the embodiments described below, and it is not essential forall of the configurations described in the embodiments to be used asmeans for solving the problems.

Embodiment 1

FIGS. 1A and 1B are plan view and a sectional view of an example of thethermal detector. FIG. 1B is a sectional view of the thermal detector,taken along line A-A′ in FIG. 1A. In FIGS. 1A and 1B, an individualthermal detector is shown, but a plurality of thermal detectors may bedisposed in the form of a matrix in order to produce the configurationof a thermal detector array (e.g., a thermal-type detection device).

The thermal detector shown in FIGS. 1A and 1B is a pyroelectric infrareddetector (a type of light sensor) 200 (however, this is only an exampleand does not limit the invention). This pyroelectric-type infraredphotodetector 200 can efficiently transfer the heat that is generated bylight absorption in the two-layer light-absorbing films 270 and 272 tothe heat-detecting element (here, a pyroelectric capacitor 230) via athermal transfer member 260 having favorable thermal transferproperties.

The thermal transfer member 260 can comprise a material (for example,AlN, AlO_(x), or other metallic compounds) that, for example, has highthermal conductivity, and is optically transmissive (for example,semi-transmissive) to the light of at least some wavelength regions (thelight of a wavelength region, in which the thermal detector hasdetection sensitivity for at least a part of a band of wavelength (widthof wavelength)) of the light. The optical transparency of the thermaltransfer member 260 will be described later with reference to FIG. 2.

The pyroelectric capacitor 230 serving as a heat-detecting elementconverts heat to electrical signals. A detection signal (for example, anelectric current signal) that corresponds to the intensity of thereceived light is thereby obtained. The pyroelectric capacitor 230serving as the heat-detecting element is formed on the support member215. Herein, the expression “on . . . ” may refer to “directly above,”or may alternatively refer to the upper part (in cases in which anotherlayer is interposed). A similarly broad interpretation is possible inother places as well. The following is a detailed description.

Example of Thermal Detector (Pyroelectric Infrared Detector)

The sectional structure will first be described with reference to FIG.1B.

Sectional Structure of Pyroelectric Infrared Detector

The pyroelectric-type infrared detector 200 that is used as the thermaldetector is constituted by a multilayer structure that is formed on asubstrate (silicon substrate) 10. Specifically, the pyroelectric typeinfrared light detector that is used as the thermal detector 200comprises a substrate (in this case, a silicon substrate) 10, astructure 100 including an insulating layer that is formed on theprimary surface (in this case, the top surface) of the substrate 10(e.g., a multilayer structure including an interlayer insulating film;refer to FIG. 6 for details concerning the multilayer structure), anetching stopper film 130 a formed on the surface of the structure 100including the insulating layer, a cavity for thermal isolation (thermalisolation cavity) 102, a support member (membrane) 215 that isconstituted by a mounting part 210 and arm parts 212 a and 212 b, apyroelectric capacitor 230 as a heat detection element that is formed onthe support member (membrane) 215, an insulating layer 250 that coversthe surface of the pyroelectric capacitor 230, a first light-absorbinglayer (e.g., an SiO₂ layer) 270, a thermal transfer member 260 (having aconnecting portion CN and a thermal collecting portion FL), and a secondlight-absorbing layer (e.g., an SiO₂ layer) 272.

The pyroelectric capacitor 230 comprises a lower electrode (the firstelectrode) 234, a pyroelectric material layer 232, and an upperelectrode (the second electrode) 236. The lower electrode of thepyroelectric capacitor 230 has an extending portion RX that extendsaround the pyroelectric material layer in plan view (in plan view asseen from the direction perpendicular to the surface of the substrate),this extending portion RX having light-reflecting properties by which atleast a part of the light that has been transmitted through a thermalcollecting portion FL of the thermal transfer member 260 is reflected.The “extending portion” can also alternatively be called a “juttingportion” or an “augmented portion.”

The first light-absorbing layer 270 is formed between the thermaltransfer member 260 (specifically, the thermal collecting portion FL ofthe thermal transfer member 260) and the extending portion RX in thelower electrode of the heat-detecting element (the pyroelectriccapacitor 230), and is connected to the thermal transfer member 260(specifically, the thermal collecting portion FL of the thermal transfermember 260).

The second light-absorbing layer 272 is formed on the thermal transfermember 260 (specifically, the thermal collecting portion FL of thethermal transfer member 260, and is connected to the thermal transfermember 260 (specifically, the thermal collecting portion FL of thethermal transfer member 260).

Namely, the lower electrode 234 comprises a material with excellentconductivity (for example, a metallic material); the light reflectanceof metallic materials and the like is generally high. Accordingly, muchof the light that is incident on the surface of the extending portion RXof the lower electrode 234, which is a constituent element of thepyroelectric capacitor 230, is reflected, this reflected light thenbeing absorbed in either the first light-absorbing layer 270 or thesecond light-absorbing layer 272. The incident light can accordingly beused without waste, and can be converted to heat. A part of the lightthat arrives at the surface of the support member 215 may also possiblybe reflected and absorbed in either the first light-absorbing layer 270or the second light-absorbing layer 272. In this regard as well, theincident light can be used efficiently.

In the example of FIGS. 1A and 1B, the extending portion RX in the lowerelectrode 234 is formed so as to jut to the periphery of the thermaltransfer member 260 in plan view. The extending portion RX can be madeto jut farther out than the periphery of the thermal transfer member260, or, conversely, can also be made to stop jutting while inside theperiphery of the thermal transfer member 260. However, the effect ofefficiently reflecting light that has been transmitted through thethermal collecting portion FL of the thermal transfer member 260 isweakened when the extending portion RX in the lower electrode 234 hastoo small a surface area. Therefore, the extending portion RX ispreferably formed to jut at least to the periphery (near the periphery)of the thermal transfer member 260, in plan view. Also, it ispreferable, from the viewpoint of effectively utilizing the incidentlight, that the extending portion RX be provided around the pyroelectricmaterial layer 232 in plan view. The extending portion RX is furtherpreferably provided around the entirety.

The lower electrode 234, comprising a metallic material and also havinghigh thermal conductivity, therefore also exerts the effect ofefficiently transferring to the pyroelectric material layer 232 heatthat, for example, has been generated at places distant from thepyroelectric material layer 232 in the first light-absorbing layer 270.That is, since the lower electrode 234, for example, extends broadly onthe support member 215, it is therefore possible to efficiently transferto the pyroelectric material layer 232 heat that has been generated in abroad range in the first light-absorbing layer 270. In this regard, itcan be said that the lower electrode 234 also serves as a thermaltransfer member (that is, as a thermal transfer member which can be saidto be, for example a second thermal transfer member, distinct from thethermal transfer member 260 formed on the upper part of the pyroelectriccapacitor 230, which can then be said to be the first thermal transfermember).

The base part (base) is constituted by the substrate 10 and themultilayer structure 100. This base part (base) supports the elementstructure 160 that includes the support member 215 and the pyroelectriccapacitor 230 in the cavity 102. In addition, a transistor, resistor, orother semiconductor element can be formed, for example, in the region ofthe silicon (Si) substrate 10 that overlaps with the heat-detectingelement (pyroelectric capacitor 230) as seen in plan view (e.g., referto the example of FIG. 6).

As described above, an etching stopper film (e.g., an Si₃N₄ film) 130 ais provided on the surface of the multilayer structure 100 that isformed on the substrate 10. In addition, etching stopper films (e.g.,Si₃N₄ films) 130 b to 130 d are formed on the back surface of thesupport member (membrane) 215. The etching stopper films 130 a to 130 dhave the role of preventing removal of layers other than the targets ofetching in the step in which the sacrificial layer (not shown in FIG. 1,refer to designation 101 in FIG. 3) is etched in order to form thecavity 102. However, the etching stopper film is not necessary, in somecases, depending on the material that constitutes the support member(membrane) 215.

In addition, the pyroelectric capacitor 230 that is part of the elementstructure 160 is supported above the cavity 102 by the support member(membrane) 215 which is also part of the element structure 160.

The support member (membrane) 215 can be formed by patterning athree-layer laminate of a silicon oxide film (SiO)/silicon nitride film(SiN)/silicon oxide film (SiO) (this is only an example and does notlimit the invention). The support member (membrane) 215 is configuredand arranged to stably support the pyroelectric capacitor 230, and thusthe total thickness of the support member (membrane) 215 is set to besufficient to provide the necessary mechanical strength.

An oriented film (not shown in the drawings) is formed on the surface ofthe support member (membrane) 215, and the pyroelectric capacitor 230 isformed on this oriented film. As described above, the pyroelectriccapacitor 230 comprises a lower electrode (first electrode) 234, apyroelectric material layer (e.g., a pyroelectric body PZT layer; leadzirconate titanate layer) 232 that is formed on the lower electrode, andan upper electrode (second electrode) 236 that is formed on thepyroelectric material layer 232.

Each of the lower electrode (first electrode) 234 and the upperelectrode (second electrode) 236 can be formed, for example, bylaminating three layers of metal film. For example, a three-layerstructure may be used in which iridium (Ir), iridium oxide (IrO_(x)) andplatinum (Pt) are formed by patterning, for example, in sequence from alocation farthest from the pyroelectric material layer (PZT layer) 232.As described above, PZT (Pb(Zi, Ti)O₃; lead zirconate titanate) may beused as the pyroelectric material layer 232.

When heat is transferred to the pyroelectric material layer(pyroelectric body), a change in electrical polarity arises in thepyroelectric material layer 232 as a result of the ensuing pyroelectriceffect (pyroelectric effect). By detecting the current that accompaniesthis change in the degree of electrical polarity, it is possible todetect the intensity of the incident light.

This pyroelectric material layer 232 can be formed into a film, forexample, by sputtering or MOCVD. The film thickness of the lowerelectrode (first electrode) 234 and the upper electrode (secondelectrode) 236 is, for example, about 0.4 μm, and the film thickness ofthe pyroelectric material layer 232 is, for example, about 0.1 μm.

The pyroelectric capacitor 230 is covered by the insulating layer 250and the first light-absorbing layer 270. A first contact hole 252 isprovided on the insulating layer 250. The first contact hole 252 is usedfor connecting the electrode 226 of the upper electrode (secondelectrode) 236 to the upper electrode (second electrode) 236.

Also, the second contact hole 254 is provided in the firstlight-absorbing layer 270 (and the insulating layer 250). The secondcontact hole 254 is provided through the first light-absorbing layer 270and the insulating layer 250. This second contact hole 254 is used inorder to connect the thermal transfer member 260 to the upper electrode236 of the pyroelectric capacitor 230. Specifically, the second contacthole 254 (where the filled portion is indicated by the referencedesignation 228 in the drawing) can be filled with the same materialthat constitutes the thermal transfer member 260 (e.g., aluminum nitride(AlN) or aluminum oxide (AlO_(x))), and, as a result, a connectingportion CN is configured in the thermal transfer member 260.

The portion of the thermal transfer member 260 that extends over thefirst light-absorbing layer 270 has a thermal collecting portion FL witha planarized surface and the connecting portion CN in the portion thatconnects the thermal collecting portion FL with the upper electrode(second electrode) 236 in the pyroelectric capacitor 230.

The thermal collecting portion FL of the thermal transfer member 260,for example, has the role of collecting the heat that has been generatedover a wide region and transferring it to the pyroelectric capacitor 230that is used as the heat-detecting element. The thermal collectingportion FL, for example, can also be formed in a configuration in whichit has a level surface on the first light-absorbing layer 270 that hasbeen planarized. In this case, the “thermal collecting portion” may alsobe referred to as a “flat part” or “planar part”.

As described above, the thermal transfer member 260 can comprise amaterial that has high thermal conductivity and is opticallytransmissive (for example, semi-transmissive) to the light of a desiredband of wavelength, and can comprise, for example, aluminum nitride(AlN), aluminum oxide (AlO_(x)), or the like. It is also possible forthe material in the thermal collecting portion FL to be different fromthe material 228 in the connecting portion CN (for example, the materialof the contact plug embedded in the contact hole 254).

FIG. 1B (as well as FIG. 1A) illustrates the existence of a relationshipW0<W1<W2, where W0 is the width of the connecting portion CN, W1 is thewidth of the pyroelectric material layer 232, and W2 is the width of thethermal collecting portion FL of the thermal transfer member 260. Thewidth of the lower electrode (first electrode) 234 of the pyroelectriccapacitor 230 is also set to be W2. In other words, as depicted in FIG.1A, the periphery (outer edge) of the thermal transfer member 260 issubstantially matched in plan view to the periphery (outer edge) of thelower electrode (first electrode) 234.

As illustrated in FIG. 1B, a distance H1 between the upper surface ofthe second light-absorbing layer 272 and the surface of the extendingportion RX of the lower electrode (first electrode) 234 of thepyroelectric capacitor 230 is set to n·(λ1/4) (“n” is an integer 1 orgreater), where λ1 is a first wavelength and λ2 is a second wavelength.A first optical resonator (a λ1/4 optical resonator) is therebyconfigured between the upper surface of the second light-absorbing layer272 and the surface of the extending portion RX of the lower electrode(first electrode) 234. Because the film thickness of the lower electrode(first electrode) 234 is sufficiently thin, the thickness thereof can beignored without any particular problem, and accordingly theabove-described distance H1 can be considered to be the total filmthickness combining the film thickness H2 of the first light-absorbinglayer 270 and the film thickness H3 of the second light-absorbing layer272.

The distance H3 between the lower surface of the second light-absorbinglayer 272 and the upper surface of the second light-absorbing layer 272(that is, the film thickness H3 of the second light absorbing layer 272)can be set to n·(λ2/4). A second optical resonator (a λ2/4 opticalresonator) is thereby configured between the lower surface of the secondlight-absorbing layer 272 and the upper surface of the secondlight-absorbing layer 272. Because the film thickness of the thermalcollecting portion FL in the thermal transfer member 260 is sufficientlythin, the thickness thereof can be ignored without any particularproblem, and accordingly the resonator length of the second opticalresonator can be considered to be the film thickness H3 of the secondlight-absorbing layer 272. The effect of constituting the first opticalresonator and the second optical resonator will be described later. Thelight-reflecting layer 235 and the thermal collecting portion FL of thethermal transfer member 260 are disposed in parallel with each other.Accordingly, a parallel between the upper surface of thelight-reflecting layer 235 and the upper surface of the secondlight-absorbing layer 272 can be maintained.

Layout Configuration of Pyroelectric Infrared Detector

Next, the layout configuration will be described with reference to FIG.1A. As shown in FIG. 1A, the support member (membrane) 215 has amounting part 210 that carries the pyroelectric capacitor 230 and twoarms that hold the mounting part 210 over the cavity (thermal isolationcavity) 102, specifically, a first arm 212 a and a second arm 212 b. Thepyroelectric capacitor 230 is formed on the mounting part 210 in thesupport member (membrane) 215. In addition, as described above, theconfiguration of the element structure 160 includes the support member(membrane) 215, the pyroelectric capacitor 230, the firstlight-absorbing layer 270, the thermal transfer member 260, and thesecond light-absorbing layer 272.

The first arm 212 a and the second arm 212 b, as described above, can beformed in long thin shapes by processing involving patterning athree-layer laminated film consisting of a silicon oxide film (SiO), asilicon nitride film (SiN), and a silicon oxide film (SiO). The reasonthat long thin shapes are produced is to increase thermal resistance andto control heat dissipation (heat release) from the pyroelectriccapacitor 230.

The wide distal end part 232 a of the first aim 212 a is supported abovethe cavity 102 by a first post 104 a (circular member as seen in planview, represented by a broken line in FIG. 1A). In addition, wiring 229a is foamed on the first arm part 212 a that connects one end (referencesymbol 228) to the lower electrode (first electrode) 234 of thepyroelectric capacitor 230 and the other end 231 a to the first post 104a.

The first post 104 a, for example, is provided between the structure 100that includes the insulating layer shown in FIG. 1B and the distal endpart 232 a of the first arm part 212 a. This first post 104 a isconstituted by a multilayer wiring structure that has been processedinto a pillar shape that is selectively formed in the cavity 102(composed of an interlayer insulating layer and a conductive layer thatconstitutes wiring for connecting the elements such as transistorsprovided on the underlying silicon substrate 10 with the pyroelectriccapacitor 230).

Similarly the second arm part 212 b is supported above the cavity 102 bya second post 104 b (in FIG. 1A, a circular member as seen in plan view,represented by a broken line). The broad distal end part 232 b in thesecond arm part 212 b is supported over the cavity 102 by a second post104 b (in FIG. 1A, a circular member as seen in a plan view, representedby a broken line). In addition, wiring 229 b is formed on the second armpart 212 b that connects one end (reference symbol 226) to the upperelectrode (second electrode) 236 of the pyroelectric capacitor 230 andthe other end 231 b to the second post 104 b.

The second post 104 b, for example, is provided between the structure100 that includes the insulating layer shown in FIG. 1B and the distalend part 232 b of the second arm part 212 b. This second post 104 b maybe constituted by a multilayer wiring structure that has been processedinto a pillar shape selectively in the cavity 102 (composed of aninterlayer insulating layer and a conductive layer that constituteswiring for connecting the elements such as transistors provided on theunderlying silicon substrate 10 with the pyroelectric capacitor 230).

In the example shown in FIG. 1A, the first post 104 a and the secondpost 104 b are used in order to hold the element structure 160 includingthe support member 215 and the pyroelectric capacitor 230 above thecavity 102. With this configuration, it is useful if a plural number ofpyroelectric capacitors 230 used as heat-detecting elements are disposedat high density in a shared cavity 102 (in other words, when forming aheat-detecting element array). However, this configuration is only anexample and does not limit the present invention. For example, in theexample shown in FIG. 6, a single space 102 is formed for each of theindividual heat-detecting elements (pyroelectric capacitor) 230, and thesupport member (membrane) 215 may be supported by the structure 100including the insulating layer surrounding the cavity 102.

In FIG. 1A, the pyroelectric capacitor 230 is disposed in a middleregion of the mounting unit 210 in the support member 215, and thepyroelectric capacitor 230 has a substantially square shape in planview. FIG. 1A illustrates the existence of a relationship W0<W1<W2,where W0 is the width in the connecting portion CN of the thermaltransfer member 260, W1 is the width of the pyroelectric material layer232 in the pyroelectric capacitor 230, and W2 is the width of thethermal collecting portion FL of the thermal transfer member 260 and thewidth of the lower electrode (first electrode) 234.

Consequently, the surface area of the collecting portion FL of thethermal transfer member 260 as seen in plan view (from a directionperpendicular to the surface of the substrate 10; i.e., as seenperpendicularly from above) is greater than the surface area of theconnecting portion CN. In addition, the surface area of the collectingportion FL of the thermal transfer member 260 as seen in plan view isgreater than the surface area of the pyroelectric capacitor 230.

In addition, as shown in FIG. 1A, the first light-absorbing layer 270and the second light-absorbing layer 272 are formed around thepyroelectric capacitor 230 used as the heat-detecting element, which ison the support member (membrane) 215, as seen in plan view.Consequently, the heat that is generated over a large region of thefirst light-absorbing layer 270 and the second light-absorbing layer 272is efficiently transmitted directly to the pyroelectric capacitor 230,or indirectly via the thermal transfer member 260.

In other words, the heat that is generated over a large region of thefirst light-absorbing layer 270 and the second light-absorbing layer 272is collected from all directions (in other words, from all sides) in thepyroelectric capacitor 230. In this case, the pyroelectric capacitor 230is disposed below the middle of the roughly square-shaped thermaltransfer member 260, as seen in plan view. Thus, the heat that iscollected via the thermal transfer member 260 from all directions istransferred to the upper electrode (second electrode) 236 of thepyroelectric capacitor 230 through the shortest possible distance viathe connecting portion CN. Thus, much of the heat is efficientlycollected from a wide area, and the heat can be transferred to the upperelectrode (second electrode) 236 of the pyroelectric capacitor 230through the shortest possible distance while minimizing loss. Thus, thephotodetection sensitivity of the thermal detector 200 can beadditionally increased. In addition, the response rate of the thermaldetector can be additionally improved.

Since the extending portion RX of the lower electrode (first electrode)234 in the pyroelectric capacitor 230 also has the effect oftransferring heat, as has been described above, the heat that isgenerated in a large region of, for example, the first light-absorbinglayer 270 is collected in the pyroelectric material layer 232 from everydirection, through the extending portion RX. The effect of efficientlytransferring to the pyroelectric material layer 232 heat that has beengenerated at places distant from the pyroelectric material 232 in thefirst light-absorbing layer 270 is also obtained.

Absorption is also more efficient in this embodiment, because heat isgenerated by the two light-absorbing films 270, 272. The heat can bedirectly transferred to the heat-detecting element 230 via the firstlight-absorbing layer 270. The thermal detector can accordingly detectat a further improved degree of sensitivity compared to the infrareddetection element recited in Japanese Patent No. 3339276 and theinfrared solid-state imaging element recited in Japanese PatentApplication Republication No. 99/31471. Also, the heat-detecting element230 is connected to the thermal transfer member 260 in this embodiment.The response speed is accordingly as high as that of the infrareddetection element recited in Patent Reference 1. The response speedobtained in this embodiment is even higher than that of the infraredsolid-state imaging element recited in Patent Reference 2, because thethermal transfer member 260 is directly connected to the heat-detectingelement 230.

Operation of Pyroelectric Infrared Detector

The thermal detector 200 according to this embodiment presented in FIGS.1A and 1B operates in the manner described below.

Namely, a part of the light (for example, infrared light) that isincident on the thermal detector 200 is first absorbed in the secondlight-absorbing layer 272, and the remainder thereof arrives at thethermal transfer member 260 without being absorbed. The thermal transfermember 260 is optically transmissive to light in a band of wavelength inwhich the thermal detector 200 has detection sensitivity, and is, forexample, translucent to infrared light. For example, a part of thearriving light is reflected in the thermal transfer member 260, and theremainder thereof is transmitted through the thermal transfer member260. The part of the light that is transmitted through the thermaltransfer member 260 is absorbed in the first light-absorbing layer 270,and the remaining light arrives at the surface of the support member(membrane) 215, as well as at the surface of the extending portion RX ofthe lower electrode (first electrode) 234 of the pyroelectric capacitor230 serving as a heat-detecting element formed on the support member(membrane) 215.

Much of (for example, the majority of) the light that is incident on theextending portion RX of the lower electrode (first electrode) 234 of thepyroelectric capacitor 230 is reflected on the surface thereof, and thenabsorbed into at least one of the first light-absorbing layer 270 andthe second light-absorbing layer 272, thus generating heat in either thefirst light-absorbing layer 270 or the second light-absorbing layer 272.In other words, the presence of the extending portion RX of the lowerelectrode (first electrode) 234 reduces the occurrence of incident lightbeing transmitted through the support member (membrane) 215 and escapingdownward; a greater amount of incident light can accordingly beconverted to heat, such that light can be used efficiently.

Light that is reflected by the surface of the support member (membrane)215 is also absorbed into at least one of the first light-absorbinglayer 270 and the second light-absorbing layer 272, thus generating heatin either the first light-absorbing layer or the second light-absorbinglayer. For example, in a case in which the first light-absorbing layer270 comprises a layer of SiO₂ (refractive index: 1.45) and the supportmember (membrane) 215 comprises a layer of SiN (refractive index: 2.0),the refractive index of the film constituting the support member(membrane) 215 (in other words, the refractive index of the supportmember 215) is greater than the refractive index of the firstlight-absorbing layer 270, and therefore almost all the light thatarrives at the support member (membrane) 215 will be reflected by thesurface of the support member (membrane) 215.

It is also effective to further provide, for example, a titanium (Ti)film, or other metal film, as a constituent element of the supportmember (membrane) 215 (particularly preferably provided to the surfaceby which light is reflected), increasing the light reflectance in thesurface of the support member (membrane) 215. The light that isreflected by the surface of the support member (membrane) 215 isabsorbed in the first light-absorbing layer 270 or the secondlight-absorbing layer 272.

The following is an example of how, in a case in which the incidentlight exhibits such behaviour as described above, heat is generated inthe first light-absorbing layer 270 and the second light-absorbing layer272, and of how the generated heat is transferred to the pyroelectriccapacitor 230, which is a heat-detecting element.

Namely, a part of the light that is incident on the thermal detector 200is first absorbed in the second light-absorbing layer 272, heat thenbeing generated in the second light-absorbing layer. Light that isreflected by the thermal transfer member 260 is also absorbed in thesecond light-absorbing layer 272, thus generating heat in the secondlight-absorbing layer 272.

A part of the light that is transmitted through (passes through) thethermal transfer member 260 is absorbed in and generates heat in thefirst light-absorbing layer 270. The remaining light arrives at thesurface of the extending portion RX of the lower electrode (firstelectrode) of the pyroelectric capacitor 230, and also at the surface ofthe support member (membrane) 215.

As described above, much of (for example, the majority of) the lightthat is incident on the surface of the extending portion RX of the lowerelectrode (first electrode) is reflected, and this reflected light isthen absorbed in the first light-absorbing layer 270 or the secondlight-absorbing layer 272. The incident light can accordingly be usedwithout waste, and can be converted to heat.

The extending portion RX of the lower electrode (first electrode) of thepyroelectric capacitor 230 also has the effect of collecting heat; heatgenerated in a wide range of the first light-absorbing layer 270 cantherefore be efficiently collected in the pyroelectric material layer232.

Since part of the light that arrives at the surface of the supportmember (membrane) 215 is also reflected, and then absorbed in the firstlight-absorbing layer 270 or the second light-absorbing layer 272, theincident light is also effectively utilized in this regard.

The heat that has been generated by the second light-absorbing layer 272is efficiently transferred to the pyroelectric capacitor 230 that isused as the heat-detecting element via the thermal transfer member 260,and the heat that has been generated by the first light-absorbing layer270 is efficiently transferred to the pyroelectric capacitor 230,directly or via the thermal transfer member 260.

Specifically, the thermal collecting portion of the thermal transfermember 260 is formed so as to broadly cover the heat-detecting element230, and thus most of the heat that is generated by the firstlight-absorbing layer 270 and the second light-absorbing layer 272 canbe transferred efficiently to the heat-detecting element, regardless ofthe site at which it was generated. For example, even heat that has beengenerated at a location distant from the pyroelectric capacitor 230 canbe efficiently transferred to pyroelectric capacitor 230, which is aheat-detecting element, via the thermal transfer member 260 having highthermal conductivity.

In addition, because the thermal collecting portion FL of the thermaltransfer member 260 and the pyroelectric capacitor 230 are connected bythe connecting portion CN of the thermal transfer member 260, the heatthat is transmitted via the thermal collecting portion FL of the thermaltransfer member 260 can be directly transmitted to the pyroelectriccapacitor 230 via the connecting portion CN. Moreover, because thepyroelectric capacitor 230 that is used as the heat-detecting element ispositioned under (directly under) the thermal transfer member 260(provided in positions that are superimposed as seen in plan view), itis possible, for example, to connect the pyroelectric capacitor 230 andthe middle part of the thermal transfer member 260 via the shortestpossible distance, as seen in plan view. Thus, the loss occurring withheat transfer can be decreased, and an increase in footprint can beminimized.

In this manner, in accordance with the thermal detector described inFIGS. 1A and 1B (in this case a pyroelectric-type infrared lightdetector), the heat that has been generated over a large region in two(a plurality of) light-absorbing layers 270, 272 can be efficientlytransferred to the pyroelectric capacitor 230 which is used as theheat-detecting element. Thus, the light detection sensitivity ofsmall-size thermal detectors (pyroelectric-type infrared photodetectors)can be greatly increased. Moreover, the time required for light transferis decreased, and so the response rate of the thermal detector(pyroelectric-type infrared photodetector) can be increased.

The light-reflecting effects and heat-collecting effects of theextending portion RX of the lower electrode (first electrode) 234 of thepyroelectric capacitor 230 also increase the detection efficiency of thethermal detector.

In addition, with the thermal detector (pyroelectric-type infraredphotodetector) described in FIGS. 1A and 1B, the first light-absorbinglayer 270 and the second light-absorbing layer 272 are formedsurrounding the pyroelectric capacitor 230 used as the heat-detectingelement as seen in plan view on the support member 215 (or the mountingpart 210 thereof). As a result, the heat that is generated over a largeregion of the first light-absorbing layer 270 and the secondlight-absorbing layer 272 is extremely efficiently transferred to thepyroelectric capacitor 230 used as the heat-detecting element, eitherdirectly or indirectly via the thermal transfer member 260. Thus, thelight detection sensitivity of the thermal detector (pyroelectric-typeinfrared photodetector) can be additionally increased, and the responserate of the thermal detector (pyroelectric-type infrared photodetector)can be additionally increased.

The thermal detector recited in FIGS. 1A and 1B (the pyroelectricinfrared detector) also has a first optical resonator for a firstwavelength λ1 configured between the surface of the secondlight-absorbing layer 272 and the surface of the extending portion RX ofthe lower electrode (first electrode) 234 of the pyroelectric capacitor230, and also has a second optical resonator for a second wavelength λ2,which is different from the first wavelength λ1, configured between thelower surface of the second light-absorbing layer 272 and the uppersurface of the second light-absorbing layer 272. Namely, the filmthicknesses of the first light-absorbing layer 270 and the secondlight-absorbing layer 272 are adjusted to constitute two opticalresonators having different resonance wavelengths.

As has been described above, the light that is reflected by theextending portion RX of the lower electrode (first electrode) 234 of thepyroelectric capacitor 230 is absorbed into at least one of the firstlight-absorbing layer 270 and the second light-absorbing layer 272, butconstituting the first optical resonator can increase the effectiveabsorptivity in each light-absorbing layer at this time.

The first optical resonator can be, for example, a so-called λ/4 opticalresonator. Namely, the film thicknesses of the first light-absorbinglayer 270 and the second light-absorbing layer 272 are adjusted suchthat the distance H1 between the surface of the extending portion RX ofthe lower electrode (first electrode) 234 of the pyroelectric capacitor230 and the upper surface of the second light-absorbing layer 272 (thetotal thickness H1 of the first light-absorbing layer 270 and the secondlight-absorbing layer 272, when the film thickness of the lowerelectrode 234 can be ignored) satisfies the relationship n·(λ1/4) (n isan integer equal to or greater than 1), where λ1 is the firstwavelength. The light of the wavelength λ1 that is incident and thelight of the wavelength λ1 that is reflected by the extending portion RXof the lower electrode 234 are thereby cancelled out due to mutualinterference, thus increasing the effective absorptivity in the firstlight-absorbing layer 270 and the second light-absorbing layer 272.

Since the extending portion RX of the lower electrode 234 comprises amaterial that is highly reflective of light, much of the incident lightcan be reflected upward, and optical resonance is accordingly prone tooccur.

As for the light that is reflected by the surface of the support member(membrane) 215, since mutual interference occurs with the incidentlight, resonance in the first optical resonator is also prone to occur.

Moreover, as described above, the light that has been reflected at thethermal transfer member 260 is absorbed at the second light-absorbinglayer 272, but by constituting the second optical resonator, effectiveabsorption in the second light-absorbing layer 272 can be increased, inthis case. A so-called λ/4 optical resonator, for example, may be usedas the second optical resonator.

Specifically, taking the second wavelength as λ2, the second opticalresonator can be constituted by setting the distance between the bottomsurface of the second light-absorbing layer 272 and the top surface ofthe second light-absorbing layer 272 (specifically, the film thicknessof the second light-absorbing layer) to n·(λ2/4). As a result, incidentlight of wavelength λ2 and light of wavelength λ2 that has beenreflected at the bottom surface of the second light-absorbing layer(interface between the first light-absorbing layer 270 and the secondlight-absorbing layer 272) are cancelled out due to mutual interference,thereby increasing the effective absorption at the secondlight-absorbing layer 272.

Moreover, by having a configuration involving two optical resonators,the wavelength bandwidth of light that can be detected by the thermaldetector can be increased as a result of peaks synthesis because aresonance peak is produced at the two different wavelengths. In otherwords, the wavelength bandwidth (wavelength range) that can be detectedby the thermal detector can be increased.

Preferred Example of Thermal Transfer Member

A preferred example of the thermal transfer member (thermal transferlayer) is described below. As described above, with the thermal detector200 of this embodiment, a structure is used in which the heat collectingportion FL in the thermal transfer member 260 is sandwiched by the firstlight-absorbing layer 270 and the second light-absorbing layer 272.Thus, in addition, the thermal collecting portion FL of the thermaltransfer member 260 can collect even heat that has been generated atpositions that are far from the pyroelectric capacitor 230 that is usedas the heat-detecting element. As a result, it is preferable for thethermal collecting portion to have a large surface area as seen in planview. Given this situation, it is preferable for the thermal transfermember 260 to be constituted by a material that is transmissive to lightand allows light of at least some of the wavelengths that are in thedesired wavelength range to pass, so that light that is incident fromabove the thermal detector 200 is absorbed by both the firstlight-absorbing layer 270 and the second light-absorbing layer 272.

Specifically, the thermal transfer member 260 is preferably constitutedby a material that has thermal conductivity and light transmissivity andhas favorable thermal transfer properties. The thermal transfer member260 can be constituted, for example, by aluminum nitride (AlN) oraluminum oxide (AlO_(x)). The aluminum oxide is also referred to asalumina, and Al₂O₃ may also be used, for example.

FIG. 2A is a diagram that show an example of the spectralcharacteristics (light reflection characteristics and light transmissioncharacteristics) of the alumina plate in the far-infrared lightwavelength range and FIG. 2B is a diagram that shows an example of thedetection sensitivity of the thermal detector when two opticalresonators are configured.

Although the far-infrared light wavelength range is not particularlystrictly defined, the wavelength range of far-infrared light isgenerally about 4 μm to about 1000 μm. Infrared light is radiated by allbodies, and bodies having high temperatures radiate intense infraredlight. The wavelength of peak radiation is inversely proportional totemperature, and the peak wavelength of infrared light radiated by abody at room temperature, 20° C., is about 10 μm.

FIG. 2A shows the reflectance and transmittance of an alumina plate inthe wavelength range of 4 μm to 24 μm. The horizontal axis is wavelength(μm), and the vertical axis is relative intensity (arbitrary units:a.u.). In FIG. 2, the characteristic line Q1 indicating transmittance isrepresented as a dashed-dotted line, and the characteristic curve Q2indicating reflectance is indicated as a solid line. Characteristiccurve Q3 which shows the results of adding the reflectance and thetransmittance is represented by a dotted line.

As shown in FIG. 2A, the reflectance varies widely in accordance withwavelength. On the other hand, the transmittance is nearly zero in thewavelength range of 6 μm and above.

Considering the transmittance and reflectance for light of wavelength 4μm, the transmittance is 0.2 (in other words, 20%), and the reflectanceis 0.5 (in other words, 50%). Considering the transmittance andreflectance for light of wavelength 12 μm, the transmittance is nearly 0(0%), and the reflectance is about 0.43 (43%).

Considering these spectral characteristics, the first wavelength λ1described above can be set to 4 μm, and the second wavelength λ2 can beset to 12 μm. In this case, if the film thickness of the firstlight-absorbing layer 270 can be 3 μm, for example, then the filmthickness of the second light-absorbing layer 272 can be 1 μm, forexample.

When alumina having the spectral characteristics shown in FIG. 2A isused as the material for the thermal transfer member 260, about 50% ofthe light having wavelengths of the first wavelength λ1 (=4 μm)contained in the incident light is reflected by the thermal transfermember 260 that is formed from alumina, and about 20% of light having awavelength of the first wavelength λ1 (=4 μm) contained in the incidentlight passes through the thermal transfer member 260.

The light of wavelength λ1 that has passed through the thermal transfermember 260 reaches the support member (membrane) 215 and is reflected atthe surface thereof, then moves upwards towards the secondlight-absorbing layer 272, where some of this light is reflected at thetop surface of the second light-absorbing layer 272 (interface betweenthe atmosphere and the second light-absorbing layer 272) and is directeddownwards again. In this manner, resonance can arise at wavelength λ1 inthe first optical resonator.

In addition, about 43% of the light of wavelength λ2 (=12 μm) containedin the incident light is reflected by the thermal transfer member 260(almost no transmitted light), and the reflected light moves upwardsthrough the second light-absorbing layer 272. Some of this light isreflected at the top surface of the second light-absorbing layer 272(interface between the atmosphere and the second light-absorbing layer272), and is again directed downwards. In this manner, resonance can bemade to arise at wavelength λ2 in the second optical resonator.

As a result of the generation of optical resonance as described above,the effective light absorption in the first light-absorbing layer 270and the second light-absorbing layer 272 can be increased.

As shown in FIG. 2B, the wavelength range in which the thermal detectorhas detection sensitivity can be increased. FIG. 2B is a diagram showingan example of the detection sensitivity of a thermal detector for a casein which two optical resonators are constituted. In the example shown inFIG. 2B, the resonance peak P1 produced by the first optical resonatorappears at wavelength λ1 (e.g., λ1=4 μm), and the resonance peak P2produced by the second optical resonator appears at wavelength λ2 (e.g.,λ2=12 μm). By synthesizing these peak characteristics, the detectionsensitivity P3 of the thermal detector 200 is widened. In other words, athermal detector 200 is realized that has detection sensitivity over abroad range of wavelengths. Similar effects can be obtained whenaluminum nitride (AlN) is used as the material for the thermal transfermember 260.

In this manner, in accordance with the thermal detector of thisembodiment, the heat that is generated at locations distant from theheat-detecting element can be efficiently and rapidly collected in thepyroelectric capacitor 230 that is used as the heat-detecting elementthrough the thermal collecting portion FL of the thermal transfer member(thermal transfer layer) 260. In addition, by utilizing interferencebetween light wavelengths (optical resonance), it is possible toincrease the effective absorption of light at the first light-absorbinglayer 270 and the second light-absorbing layer 272. It is also possibleto widen the wavelength range in which the thermal detector hasdetection sensitivity.

Thermal Detector Manufacturing Method

The thermal detector manufacturing method is described below withreference to FIGS. 3 to 5. First, FIGS. 3A to 3E will be discussed.FIGS. 3A to 3E are diagrams that show the steps of the thermal detectormanufacturing method up until formation of the first light-absorbinglayer.

In the step shown in FIG. 3A, a silicon substrate (which may haveelements such as transistors) is prepared, and a structure 100 includingan insulating layer (e.g., a multilayer wiring structure) is formed onthe silicon substrate 10. An etching stopper film 130 a is then formedon the structure 100 including the insulating layer, and a sacrificiallayer (e.g., an SiO₂ layer) 101 is then formed.

In the step of FIG. 3B, an etching stopper film 130 b is formed on thesacrificial layer 101. Next, a thick film that will serve as the supportmember (membrane) 215 (e.g., a thick film composed of a three-layerlaminated film) is formed.

In the step of FIG. 3C, the support member (membrane) 215 is laminatedwith the lower electrode (first electrode) 234, the pyroelectricmaterial layer (PZT layer) 232, and the upper electrode (secondelectrode) 236, forming the pyroelectric capacitor 230 serving as theheat-detecting element. At this time, the lower electrode (firstelectrode) 234 of the pyroelectric capacitor 230 is formed so as to havean extending portion RX that extends on the support member (membrane)215.

The method for forming the pyroelectric capacitor 230, for example, canbe an atomic layer CVD method. Next, the insulating layer 250 is formedso that it covers the pyroelectric capacitor 230. The insulating layer250 can be formed, for example, by a CVD method. Next, the insulatinglayer 250 is patterned.

In the step of FIG. 3D, the first contact hole 252 is formed in theinsulating layer 250 that covers the pyroelectric capacitor 230, and ametal material layer is then deposited, whereupon the metal materiallayer is patterned in order to form the electrode (and wiring) 226 thatconnects with the upper electrode (second electrode) 236. In the step ofFIG. 3D, wiring (not shown in) and an electrode that connects to thelower electrode (first electrode) are formed together.

In the step of FIG. 3E, the first light-absorbing layer (e.g., SiO₂layer) 270 is formed by a CVD method. Next, this surface is planarizedby, for example, chemical mechanical polishing (CMP).

FIGS. 4A to 4C are diagrams illustrating the principal steps in themethod for producing the thermal detector, until the patterning of thefirst light-absorbing layer and the second light-absorbing layer. In thestep of FIG. 4A, a second contact hole 254 is formed in the firstlight-absorbing layer 270. A thermal transfer member (heat transferlayer) 260 is then formed by the subsequent deposition and patterning ofa material that has high thermal conductivity and optical transparency,such as aluminum oxide (alumina: AlO_(x)), or aluminum nitride (AlN).The thermal transfer member 260 possesses a thermal collecting portionFL and a connecting portion CN. The second contact hole 254 is filled inwith alumina or another material. The portion 228 that is filled in withthe alumina or other material constitutes the connecting portion CN. Thelight-reflecting layer 235 and the thermal collecting portion FL of theheat transfer member 260 are disposed in parallel with each other.

In the step of FIG. 4B, a material layer that will form the secondlight-absorbing layer (e.g., SiO₂ layer) is deposited and patterned onthe first light-absorbing layer 270. As a result, the secondlight-absorbing layer 272 is formed. In the step of FIG. 4C, the firstlight-absorbing layer 270 is patterned.

FIGS. 5A and 5B are diagrams that show the steps up to completion of thethermal detector in the thermal detector manufacturing method. In thestep of FIG. 5A, the support member (membrane) 215 is patterned. As aresult, the mounting part 210, the first arm part 212 a, and the secondarm part 212 b are formed. In FIG. 5A, the reference symbol OP is usedfor the portions that are removed by patterning (openings).

In the step of FIG. 5B, the sacrificial layer 101 is selectively removedby, for example, wet etching. As a result, the cavity (thermal isolationcavity) 102 is formed. The mounting part 210 of the support member 215is separated from the base part (substrate 10, structure 100 includinginsulating layer, and etching stopper film 130 a) by the cavity 102.Consequently, release of heat through the support member 215 isinhibited. The thermal detector is completed in this manner.

Embodiment 2

Referring now to FIG. 6, a thermal detector in accordance Embodiment 2will now be explained. In view of the similarity between the first andsecond embodiments, the parts of the second embodiment that are similaror identical to the parts of the first embodiment will be given the samereference numerals as the parts of the first embodiment. Moreover, thedescriptions of the parts of the second embodiment that are identical tothe parts of the first embodiment may be omitted for the sake ofbrevity.

FIG. 6 is a diagram showing another example of the thermal detector.With the thermal detector 200 shown in FIG. 6, the cavity 102 is formedfor each individual heat-detecting element, and the support member(membrane) 215 is supported by the structure (part of the base part)that surrounds the cavity 102. In addition, a circuit constituentelement (in this case, a MOS transistor) is formed in the regionoverlapping the heat-detecting element as seen in plan view. This MOStransistor is connected via multilayer wiring to the pyroelectriccapacitor 230 that is used as the heat-detecting element. In the exampleof FIG. 6, the thermal transfer member 260 is utilized as wiring.

Specifically, a source layer (S) and a drain layer (D) are formed in thesubstrate (silicon substrate) 10. In addition, a gate insulating filmINS and a gate electrode G (e.g., a polysilicon gate electrode) areformed on the substrate 10. As a result, a MOS transistor that serves asthe circuit constituent element is formed.

The structure 100 including the insulating layer is formed on thesubstrate 10. The base (base) is constituted by the substrate 10 and thestructure 100 including the insulating layer.

The structure 100 including the insulating layer is constituted by amultilayered structure, more specifically, a multilayer wiringstructure. The multilayer wiring structure comprises a first insulatinglayer 100 a, a second insulating layer 100 b, a third insulating layer100 c, a first contact plug CP1, a first layer wiring M1, a secondcontact plug CP2, a second layer wiring M2, and a third contact plugCP3. Part of the third insulating layer 100 c is selectively removed toform the cavity (thermal isolation cavity part) 102.

The pyroelectric capacitor 230 is formed as the heat-detecting elementon the mounting part 210 of the support member (membrane) 215. Inaddition, the thermal transfer member 260 is formed between the firstlight-absorbing layer 270 and the second light-absorbing layer 272.

The element structure 160 is constituted by the support member(membrane) 215, the pyroelectric capacitor 230, the firstlight-absorbing layer 270, the second light-absorbing layer 272, thethermal transfer member 260, a fourth contact plug CP4, a third layerwiring M3, and a fifth contact plug CP5. As described above, the thermaltransfer member 260 also functions as part of the wiring that connectsthe pyroelectric capacitor 230 that is used as the heat-detectingelement to the other elements (in this case, a CMOS transistor that isformed on the substrate 10).

Specifically, as described above, the thermal transfer member 260 can beconstituted by a metal compound such as AlN or AlO_(x), but becausematerials having metals as primary components also have favorableelectrical conductivity, the thermal transfer member 260 can also beutilized as wiring (or part of the wiring) that connects theheat-detecting element to other elements. By using the thermal transfermember 260 as wiring, it is not necessary to provide separate wiring,and the production steps can be simplified.

Thermal Detection Device

FIG. 7 is a circuit diagram that shows an example of a circuitconfiguration for the thermal detector (thermo-optical detection array)including the thermal detector according to any of the illustratedembodiments. In the example of FIG. 7, a plurality of photodetectingcells (specifically, thermal detectors 200 a to 200 d) are disposedtwo-dimensionally. In order to select single photodetecting cells fromamong the plurality of photodetecting cells (thermal detectors 200 a to200 d), scan lines (W1 a, W1 b, etc.) and data lines (D1 a, D1 b, etc.)are provided.

The thermal detector 200 a that serve as a single photodetecting cellhas an element-selection transistor M1 a and a piezoelectric capacitorZC that serves as the thermo-optical detecting element 5. The potentialrelationship of the two poles of the piezoelectric capacitor ZC can beinverted by switching the potential that is applied to PDr1 (byinverting this potential, it is not necessary to provide a mechanicalchopper). Other photodetecting cells are similarly configured.

The potential of the data line D1 a can be initialized by turning on areset transistor M2. When reading a detection signal, the readtransistor M3 is ON. The current that is generated as a result of thepyroelectric effect is converted to voltage by an I/V conversion circuit510, amplified by an amplifier 600, and converted to digital data by anA/D converter 700.

In this embodiment, a plurality of thermal detectors is disposedtwo-dimensionally (for example, disposed in the form of an array alongtwo respective perpendicular axes (X-axis and Y-axis)), therebyrealizing a thermal detection device (thermal-type optical arraysensor).

Electronic Instrument

FIG. 8 is a diagram showing an example of the configuration of anelectronic instrument. Examples of the electronic instrument include aninfrared sensor device, a thermographic device, and an on-boardautomotive night-vision camera or surveillance camera.

As shown in FIG. 8, the electronic instrument comprises an opticalsystem 400, a sensor device 410 (corresponding to the thermal detector200 in the previous embodiment), an image processing part 420, aprocessing part 430, a memory component 440, an operation component 450,and a display part 460. The electronic instrument of this embodiment isnot restricted to the configuration of FIG. 8, and various modifiedembodiment are possible in which some of the constituent elements (e.g.,the optical system, operational, part, or display part) are omitted andother constituent elements are added.

The optical system 400 includes one or a plurality of lenses and drivingparts for driving these lenses. Imaging and the like of the subject iscarried out on the sensor device 410. In addition, focus adjustment maybe carried out as necessary.

The sensor device 410 has a configuration in which the photodetectors ofthe embodiments described above are laid out two-dimensionally, and aplurality of lines (scan lines (or word lines)) and a plurality ofcolumns (data lines) are provided. The sensor device 410 can alsocomprise line selection circuits (line drivers), a read circuit forreading data from the photodetectors via the columns, an A/D converter,and the like, in addition to the photodetectors that are laid outtwo-dimensionally. Because data is sequentially read from photodetectorsthat are laid out two-dimensionally, a captured image of the subject canbe processed.

Based on the digital image data (pixel data) from the sensor device 410,the image processing part 420 carries out various image processingoperations such as image correction processing. The image processingpart 420 corresponds to the control part that processes the output ofthe sensor device 410 (thermal detector 200). The processing part 430carries out control of the respective elements of the electronicinstrument and overall control of the electronic instrument. Thisprocessing part 430 is realized, for example, in a CPU or the like. Thememory component 440 stores various types of information, and, forexample, functions as a work space for the processing part 430 or theimage processing part 420. The operation component 450 is used as aninterface for a user to operate the electronic instrument and can beworked, for example, in the form of various buttons, a GUI (graphicaluser interface) screen, or the like.

The display part 460 displays the GUI screen, images that have beencaptured by the sensor device 410, and the like, and is worked in theform of various types of displays, such as a liquid crystal display ororganic EL display.

By using the thermal detector of a single cell as a sensor such as aninfrared light sensor in this manner and by disposing the thermaldetector of each cell along two perpendicular axes, a sensor device(thermo-optical detecting device) 410 can be configured. When this isdone, a thermal (light) distribution image can be captured. By usingthis sensor device 410, it is possible to configure an electronicinstrument such as a thermographic device, or an on-board automotivenight-vision camera or surveillance camera.

As described previously, the thermal detector according to the presentinvention has high light detection sensitivity. Thus, the performance ofthe electronic instrument in which the thermal detector is mounted isincreased.

FIG. 9 is a diagram showing another example of the configuration of theelectronic instrument. The electronic instrument 800 of FIG. 9 comprisesa thermal detector 200 and an acceleration detection element 503 whichare mounted in a sensor unit 600. The sensor unit 600 also can carry agyro sensor or the like. Various types of physical quantities can bemeasured by the sensor unit 600. The various detection signals that areoutput from the sensor unit 600 are processed by a CPU 700. The CPU 700corresponds to the control part for processing the output of the thermaldetector 200.

As described above, in accordance with at least one embodiment of thepresent invention, for example, the detection sensitivity of a thermaldetector can be dramatically improved.

In addition, in the embodiments described above, although a pyroelectriccapacitor is used as the heat-detecting element, a thermopile element orbolometer element may be used instead.

In addition, in the embodiments described above, an infrared detectorthat detects infrared light is used as an example of a thermal detector.However, it will be apparent from this disclosure that the thermaldetector according to the present invention may be configured andarranged to detect other type of light such as terahertz light, forexample.

In addition, in the embodiments described above, an infrared detectorthat detects infrared light is used as an example of a thermal detector.However, it will be apparent from this disclosure that the thermaldetector according to the present invention may be configured andarranged to detect other type of light such as terahertz light, forexample.

General Interpretation of Terms

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Also as used herein to describe theabove embodiments, the following directional terms “top”, “bottom”,“upper”, “lower”, “forward”, “rearward”, “above”, “downward”,“vertical”, “horizontal”, “below” and “transverse” as well as any othersimilar directional terms refer to those directions of the thermaldetector when the thermal detector is oriented as shown in FIG. 1B.Finally, terms of degree such as “substantially”, “about” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.For example, these terms can be construed as including a deviation of atleast ±5% of the modified term if this deviation would not negate themeaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents. All modificationssuch as described above may be understood to fall within the scope ofthe invention. Terms disclosed together with different equivalent orbroader terms in at least one instance in the specification or drawings,for example, may be replaced by these different terms at any place inthe specification or drawings.

1. A thermal detector comprising: a substrate; a support membersupported on the substrate so that a cavity is formed between thesubstrate and the support member; a heat-detecting element formed on thesupport member and having a structure in which a pyroelectric materiallayer is disposed between a lower electrode and an upper electrode; alight-absorbing layer formed on the heat-detecting element; and athermal transfer member including a connecting portion connected to theheat-detecting element and a thermal collecting portion disposed insidethe light-absorbing layer and having a surface area larger than asurface area of the connecting portion as seen in plan view, the thermalcollecting portion being optically transmissive at least with respect tolight of a prescribed wavelength, the lower electrode having anextending portion extending around the pyroelectric material layer asseen in plan view, and the extending portion having light-reflectingproperties by which at least a part of the light transmitted through thethermal collecting portion of the thermal transfer member is reflected.2. The thermal detector according to claim 1, wherein thelight-absorbing layer is disposed on the support member around theheat-detecting element.
 3. The thermal detector according to claim 2,wherein the light-absorbing layer has a first light-absorbing layercontacting the thermal transfer member and disposed between the thermaltransfer member and the extending portion of the lower electrode of theheat-detecting element, and a second light-absorbing layer contactingthe thermal transfer member and disposed on the thermal transfer member.4. The thermal detector according to claim 3, wherein a first opticalresonator for a first wavelength is formed between a surface of theextending portion of the lower electrode and an upper surface of thesecond light-absorbing layer, and a second optical resonator for asecond wavelength that is different from the first wavelength is formedbetween a lower surface of the second light-absorbing layer and theupper surface of the second light-absorbing layer.
 5. The thermaldetector according to claim 1, wherein the thermal transfer member alsoserves as wiring that electrically connects the heat-detecting elementto another element.
 6. A thermal detection device comprising a pluralityof the thermal detectors according to claim 1 arrangedtwo-dimensionally.
 7. A thermal detection device comprising a pluralityof the thermal detectors according to claim 2 arrangedtwo-dimensionally.
 8. A thermal detection device comprising a pluralityof the thermal detectors according to claim 3 arrangedtwo-dimensionally.
 9. A thermal detection device comprising a pluralityof the thermal detectors according to claim 4 arrangedtwo-dimensionally.
 10. A thermal detection device comprising a pluralityof the thermal detectors according to claim 5 arrangedtwo-dimensionally.
 11. An electronic instrument comprising: the thermaldetector according to claim 1; and a control part configured to processan output of the thermal detector.
 12. An electronic instrumentcomprising: the thermal detector according to claim 2; and a controlpart configured to process an output of the thermal detector.
 13. Anelectronic instrument comprising: the thermal detector according toclaim 3; and a control part configured to process an output of thethermal detector.
 14. An electronic instrument comprising: the thermaldetector according to claim 4; and a control part configured to processan output of the thermal detector.
 15. An electronic instrumentcomprising: the thermal detector according to claim 5; and a controlpart configured to process an output of the thermal detector.
 16. Athermal detector manufacturing method comprising: forming a structureincluding an insulating layer on a surface of a substrate; forming asacrificial layer on the structure including the insulating layer;forming a support member on the sacrificial layer; forming on thesupport member a heat-detecting element having a structure in which apyroelectric material layer is disposed between a lower electrode and anupper electrode, the lower electrode having an extending portionextending around the pyroelectric material layer as seen in plan view,and the extending portion having light-reflecting properties by whicharriving light is reflected; forming a first light-absorbing layer so asto cover the heat-detecting element, and planarizing the firstlight-absorbing layer; forming a contact hole in a portion of the firstlight-absorbing layer, subsequently forming a material layer which isthermally conductive and optically transmissive at least with respect tolight of a prescribed wavelength, and patterning the material layer toform a thermal transfer member having a connecting portion that connectsto the heat-detecting element and a thermal collecting portion having asurface area greater than that of the connecting portion as seen in planview; forming a second light-absorbing layer on the firstlight-absorbing layer; patterning the first light-absorbing layer andthe second light-absorbing layer; patterning the support member; andremoving the sacrificial layer to form a cavity between the supportmember and the structure including the insulating layer formed on thesurface of the substrate.
 17. The thermal detector according to claim 1,wherein the thermal detector is configured and arranged to detectinfrared light.
 18. The thermal detector according to claim 1, whereinthe thermal detector is configured and arranged to detect terahertzlight.
 19. The thermal detection device according to claim 6, whereinthe thermal detectors are configured and arranged to detect infraredlight.
 20. The thermal detection device according to claim 6, whereinthe thermal detectors are configured and arranged to detect terahertzlight.